The invention relates to beverage containers and more particularly to beverage containers which are vented for the purpose of reducing negative pressure or vacuum which builds up inside the container when a beverage is being consumed therefrom.
A large variety of beverage containers are constructed with a small opening or drinking spout through which the fluid contents can be extracted. The opening is adapted so that a person can place their mouth over the opening thus forming a seal around the opening. Examples of these types of beverage containers include: a soda-pop bottle having a small annular opening; a drinking cup or spill-proof cup having a cover formed with a drinking spout; and, a nipple-equipped baby bottle. As the fluid contents are being consumed from one of these beverage containers, a negative pressure or vacuum builds up within the container making it necessary to interrupt drinking long enough to allow air to enter into the container equalizing the pressure between the outside and inside atmospheres. This interruption causes inconvenience for adult drinkers and makes it difficult for babies to continue feeding. Numerous solutions have been proposed whereby the beverage container is vented to relieve the buildup of negative pressure. As one would expect, most of the solutions are directed to spill-proof cups or baby bottles for feeding infants.
A number of solutions rely on complicated mechanical valves such as that disclosed in U.S. Pat. No. 5,079,013 to Belanger. Belanger discloses a dripless baby bottle vented by means of two spring-biased check valves. Generally speaking, mechanical valves require a number of parts which make such containers difficult to manufacture, assemble and clean.
A different type of solution is disclosed in U.S. Pat. No. 4,865,207 to Joyner wherein a vent made from a woven microporous membrane allows air to pass into a baby bottle. The thin membrane is enclosed between two plastic grid plates that provide structural support and protection for the membrane. The membrane assembly is then fastened against the bottom of the baby bottle by a threaded screw cap. These membranes typically have from one million to nine million pores per square inch (a macroporous vent will have substantially less than one million pores per square inch). The large number of micropores increase the surface area susceptible to oxidatiot, contamination and wetting. Furthermore, the small pores tend to retain surfactants after washing with surfactants. The residual surfactants reduce surface tension making the membrane susceptible to wetting and leaking. Due to the thinness of the fabric, the membrane can be easily damaged. The large number of parts involved also make the container more difficult to manufacture, assemble and clean.
Another solution involves a baby bottle with a vent consisting of a pressure equalizing apertured elastomeric diaphragm member as disclosed in U.S. Pat. No. 5,499,729 to Greenwood. The elastomeric diaphragm is held against the bottom of the bottle by a screw cap. During feeding, negative pressure forces the diaphragm to stretch inward whereby small holes in the diaphragm open up allowing air to pass into the bottle. The diaphragm must be removed as a separate piece for cleaning. Again, the screw cap and diaphragm comprise additional structural elements that make the bottle more expensive to manufacture.
Finally, U.S. Pat. No 5,339,971 to Rohrig, discloses a one piece molded baby bottle in which 150 to 200 pores are burned into the base of the bottle by means of a laser. The diameter of the pore openings on the inside of the bottle wall range from 3 to 7 micrometers which is small enough to prevent the passage of water but large enough to allow the passage of air under negative pressure. The diameter of the pore openings on the outside surface of the bottle are from 50 to 100 micrometers such that each pore forms a conical shaped channel connecting the inside and outside surfaces. This baby bottle is easier to clean than the previously described bottles and requires no moving parts, but the manufacturing process related to burning in the large number of pores is obviously complicated and expensive. Furthermore, the small pore openings are susceptible to oxidative abrasion. Once the pore openings become abraded, the fluid contents can leak out.
In view of the shortcomings associated with each of the previous examples, a need still exists for a durable, one piece, vented beverage container that is easy to clean, resistant to corrosion and contamination, and simple to manufacture. The present invention is believed to meet this need.
In accordance with the invention, a beverage container is provided with a hydrophobic vent consisting of a rigid disc-shaped piece of macroporous plastic being 0.025xe2x80x3 to 0.25xe2x80x3 thick and having pore sizes averaging from 7-350 microns. The vent can be welded, molded or secured to the sidewall, bottom or cap of a plastic beverage container thus eliminating all moving parts. The macroporous plastic is resistant to oxidative abrasion, contamination and wetting and is strong enough to resist breakage. In one embodiment a baby bottle is provided which consists of a plastic bottle body, a nipple, and means for fastening the nipple to the bottle body. The bottle body is provided with a macroporous plastic vent which can be welded, molded or secured to the sidewall or bottom of the bottle body thus eliminating all moving parts. The bottle body can be washed repeatedly as a single unit with the vent intact.